1. Field of the Invention
The present invention relates to a method of and apparatus for inputting graphic data provided in the form of a set of segments, to convert the same into image data for use in filling the inner or outer region of a graphic figure whose contour line is expressed by the segments.
2. Description of Backqround Arts
In the printing field, the inner or outer region of a graphic figure is often filled with a monochromatic color to produce a cut mask or a pattern mask for use in making a printed wiring board.
In a conventional filling process, a cutting machine is employed. For example, consider a mask film 2 shown in FIG. 28A, in which the inner region of the graphic FIG. 1 should be filled with a monochromatic color. In manufacturing the mask film 2, data expressing segments 3a-3d (FIG. 28B) defining the contour line of the graphic FIG. 1 are prepared by means of a computer aided design technique (CAD). In FIG. 28B, the segments 3a-3d are illustrated as vectors in order to indicate their respective directions. The data expressing the segments 3a-3d are then delivered to a cutting machine (not shown). The cutting machine automatically cuts a peel off film 4 shown in FIG. 28C to form slits 5a-5d thereon corresponding to segments 3a-3d.
A part of the peel off film 4 corresponding to the inner region 6 (FIG. 28D) surrounded by the slits 5a-5d is then manually removed to obtain a cut mask film in which only the inner region 6 is transparent. The cut mask film is inversely printed on another film through a contact printing process to obtain the mask film 2 (FIG. 28A) in which only the inner region of the graphic figure 1 is opaque.
In another conventional technique, a photoplotter is employed. To manufacture the mask film 2 with this technique, graphic data expressing the graphic FIG. 1 are prepared by means of CAD (as in the first technique). However, the graphic data are not identical to those in the first technique in that they express a set of segments 7 (FIG. 29A) filling the inner region 6 rather than the segments 3a-3d defining the contour line. The graphic data expressing the segments 7a are then delivered to the photoplotter (not shown).
The photoplotter scans the surface of a photosensitive film with a light beam along the segments 7 while controlling the light beam so that it is in 0N state on the segments 7 and in OFF state on the other region, whereby the photosensitive film 2 shown in FIG. 29B is exposed along the trace 8 of the exposure light beam. The exposed photosensitive film 2 is then developed to obtain the desired film 2 of FIG. 28A having the filled region.
The first conventional technique (employing the cutting machine) has an advantage in that the graphical data can be easily prepared since the first technique requires only the data expressing the segments 3a-3d which define the contour line of the graphical FIG. 1. The segments 3a-3d may be crossed without terminating at a common point, since the respective parts of the slits 5a-5d extending over the other slits do not substantially hinder the opaque character of the outer region in the film 4. However, the technique has a disadvantage in that an operator must be skilled to manually take off the region 6 of the peel off film 4. Further, the efficiency of the manual operation is low and the desired film cannot be easily obtained.
The second conventional technique does not require a manual operation. The desired film 2 can be obtained automatically. However, since the diameter of the exposure beam spot is small, it takes a long time to fill the inner region of a graphic figure--particularly when the inner region has a relatively wide area. Sometimes, a portion between adjacent segments is left unfilled even after scanning is completed. Further, it takes a long time to prepare the graphic data with CAD.
Under the circumstances, it is desirable to develop a system in which graphic data is prepared through CAD or the like only for a contour line. Further, it is desirable to develop a system in which filling is automatically conducted at a high speed. The desirable system may be constructed with a laser plotter in which exposure scanning with a laser beam is controlled according to run length data To obtain the run length data, graphic data must be prepared which includes information with respect to a contour line which can be drawn with a single stroke, as shown in FIG. 28E as well as information indicating whether the inner region of the contour line is to be filled or to be left unfilled. A contour line which can be drawn with a single stroke is hereinafter referred to as a "single stroke contour line".
Although such graphic data can be prepared through CAD dedicated to the laser plotter, it is desired to obtain the graphic data from graphic data prepared for the cutting machine. However, a contour line expressed by the graphic data prepared for the cutting machine is not always a single stroke contour line. Therefore, when the graphic data for the cutting machine is employed for controlling the laser plotter, it is necessary to distinguish the inner region from the outer region of the graphic FIG. 1 on the basis of the graphic data indicating the segments 3a-3d of FIG. 28B which imperfectly express the contour line. The distinction process will be complicated since graphic figures have many variations. Thus, the desired system will not be obtained unless a technique is developed in which imperfection in segment connection is detected and a single stroke contour line is reproduced at high efficiency and high speed.